1. Field of the Invention
The present invention relates to a thermoelectric material and a process for production thereof. More particularly, the present invention relates to a thermoelectric material having high performance and a process in production steps and is industrially advantageous.
2. Description of the Related Arts
A thermoelectric material for thermoelectric power generation utilizing the Seebeck effect or thermoelectric cooling utilizing the Peltier effect is widely used in various fields, for example, thermoelectric power generation, temperature sensors, thermostatic apparatus in a semiconductor production process, and cooling of electronic devices. For production of such thermoelectric materials, various methods have heretofore been proposed. For example, (1) a crystal ingot production method in which starting materials are alloyed by melting, converted into an ingot and then sliced, (2) a powder sintering method in which a starting material powder or starting materials which have been alloyed by melting and then powdered, are molded and sintered, and sliced, if necessary, (3) a polycrystallization-zone melting method, (4) an amorphous production method, and (5) a thin or thick film production method are known.
These methods, however, have problems in that the process is complicated, a long term treatment of alloying by melting at high temperatures is needed, productivity is low and energy consumption is high. In methods including a slicing step, the slice loss results, and in the polycrystallization-zone melting method, undesirable electrical or mechanical anisotropy result from crystallization. Moreover, for the reason that super-small sized elements are difficult to produce, the methods are used only in limited fields.
The conventional methods are limited in molding methods and thus have an intrinsic problem that makes it difficult to get desirable molded shapes by various molding methods.
Japanese Patent Application Laid-Open No. 143383/1984 discloses a method in which mixture of a telluride lead compound and a manganese-based metal powder is molded and sintered in order to overcome the above problems. This method, however, is not quite satisfactory. That is, the conventional methods use a alloyed powder material to mix and mold, and only powders of several tens or several hundreds of microns are used.